1. Field of the Invention
The present disclosure relates to a rate matching device and a rate matching method, and particularly to a rate matching device and a method for applying a rate matching technique when a high speed data processing technique is applied in a communications system.
2. Discussion of the Background
The Universal Mobile Telecommunications Service (UMTS) system is a mobile communications system based on the Global System for Mobile communications (GSM) and the General Packet Radio Service (GPRS), and is a third-generation mobile communications system that uses code division multiple access (CDMA) technology.
This UMTS system employs a virtual connection concept of a packet switching method using a packet protocol such as the Internet Protocol (IP). Through the UMTS system, users of mobile phones or computers may receive more consistent services, and may be capable of transmitting packet-based texts, digital voice or video, and multimedia data at a speed of 2 Mbps or more.
The High-Speed Uplink Packet Access (HSUPA) technique of the 3GPP Physical Layer for the UMTS is designed to improve data transmission speed using the enhanced uplink dedicated channel (E-DCH). The uplink dedicated channel supports the Hybrid automatic retransmission request (HARQ) technique, which is designed to provide more stable high-speed data transmission.
The HARQ is a technique for retransmitting packets to correct a packet error when the error occurs in the initially transmitted data packets. This technique may be classified as the chase combining (CC) technique of retransmitting the packets having the same format as the initially transmitted format when an error occurs, or the incremental redundancy (IR) technique of retransmitting the packet having a format different from the initially transmitted format when an error occurs.
The HARQ technique supports base station-based scheduling and Transmission Time Interval (TTI) of 10 ms and 2 ms, and thus may control the Physical Layer with 2 ms intervals. Moreover, since the HARQ technique separately imposes a power weight on each enhanced dedicated physical control channel (EDPCCH) or supports a spreading factor (SF) with a channel bit rate of 1920 kbps, more data may be transmitted in shorter time.
Rate matching is used for matching a volume of data to be transmitted per TTI to the maximum transmission volume of actual physical channels. Upon executing the rate matching, an operational algorithm is used for puncturing or repeating the bits of a transport block on a transport channel (TrCH) in accordance with the bit size of a physical channel frame that is used as a transmission unit on the corresponding physical channel (PhCH).
FIG. 1 is a flowchart illustrating a conventional rate matching method. FIG. 2 is a graph for explaining the conventional rate matching method of FIG. 1.
The rate matching method includes a step S110 of determining rate matching parameters, a step S120 of determining a rate matching pattern using the rate matching parameters, and a step S130 of executing the rate matching.
In the step S110 of determining the rate matching parameters, bits ΔNi,j to be punctured or repeated are calculated in accordance with the number of bits transportable to the physical channel. Then, other rate matching parameters are calculated from the bits ΔNi,j.
The rate matching parameters are defined according to a telecommunications standard, such as the 3GPP standard TS 25.212, and can include an initial value (e_ini), an increment (e_plus) and a fixed decrement (e_minus) of a variable e used in an algorithm for determining the rate matching pattern. The rate matching pattern indicates whether the bits are punctured or repeated using the rate matching parameter. Once the rate matching parameters are calculated, the rate matching pattern may be determined using an algorithm defined in the 3GPP standard TS 25.212.
FIG. 2 shows an example in which the fifth bit and the ninth bit are punctured from an input bit index by using the rate matching algorithm when e<0.
In the step S130 of executing the rate matching pattern, bit puncturing or bit repeating in accordance with the rate matching pattern is executed to generate a rate matching block.
Specifically, the conventional rate matching algorithm determines the rate matching pattern, and then determines the bit repeating in the rate matching block if ΔNi,j>0, and determines the bit puncturing in the rate matching block if ΔNi,j<0. This algorithm may cause faster or more frequent bit puncturing to be executed in the rate matching block by decreasing the initial value (e_ini) of the variable e by the fixed decrement (e_minus). Upon executing the bit puncturing, retransmission is then executed for avoiding and/or correcting data bits where an error occurs. Accordingly, more rate matching algorithms are consequently executed. Moreover, time consumed to execute mapping between the transport channels and the physical channels is increased, as the bit puncturing may be executed more frequently. On the contrary, when the bit repeating is executed, the rate matching algorithm for executing the bit repeating may be applied once.